Many electronic apparatus require memory devices that have high capacity and speed to process increased data volumes. The capacity of a memory device increases in proportion to advances in process technologies that allow for their gradual miniaturization. A demand exists, consequently, for a memory device that can maximize storage capacity on a limited area. Various efforts are underway to meet such a demand. One of these efforts involves storing N-bit data (N≧2), instead of 1-bit data, in a cell. Doing so allows fabrication of a memory device that has double or more integration density using the existing process technology. Another effort involves packing two or more integrated circuit chips (or dies) in a single package. Since a low capacity chip is small, a distance between a lead frame and a chip pad is sufficient to ensure appropriate wire bonding. But, since a high capacity chip is large, a distance between a lead frame and a chip pad is limited.
A data input/output speed of a semiconductor memory device varies with a bit organization. For example, comparing a device having an X8 bit organization and another having an X16 bit organization, both with the same capacity, the latter can achieve twice the data input/output speed of the former. Memory devices are constructed with either X8 or X16 bit organization according to the required application. But a typical wafer-level memory device is not. That is, the wafer-level device may alternately be constructed to support the X8 or X16 bit organizations. Once built, the memory device is at a pack-level selected to have X8 or X16 bit organization according to the required application. And the package must conform with the bit organization selected for the memory device.
A package pin configuration is shown in FIG. 1. In a memory device having the X8 bit organization, data bits I/00˜I/07 are input/output through data pins 29, 30, 31, 32, 41, 42, 43, and 44. In a memory device having the X16 bit organization, data bits I/O0–I/O15 are input/output through data pins 26, 27, 28, 29, 30, 31, 32, 33, 40, 41, 42, 43, 44, 45, 46, and 47. Since data bits are input/output through different pins according to a bit organization, data pads must be connected to different pins according to the bit organization. As shown in FIG. 2, in a case where a memory device has, for example, an X8 bit organization, data pins 29, 30, 31, 32, 41, 42, 43, and 44 must be electrically connected to corresponding data pads P1, P3, P5, P7, P15, P17, P19, and P21. In a case where the memory device has an X16 bit organization, data pins 26–33 and 40–47 must be electrically connected to corresponding data pads P1–P8 and P40–P47, respectively.
In the X16 bit organization, data pins must be electrically connected to adjacent data pads. In the X8 bit organization, data pins must be electrically connected to non-adjacent (or removed) data pins. This example assumes the memory device having the X8 and X16 bit organizations is packed using one package.
Since a low capacity chip is small in size, the distance between a lead frame of a package and a chip pad is sufficiently secured to perform a wire bonding. Conversely, since a high capacity chip is large in size, a distance between a lead from and a chip pad of a package is limited by package size. Thus, when a data pin (e.g., 29) is connected to a corresponding data pad (e.g., P1), the wire bonding can run over an adjacent data pad (e.g., P2). It may be necessary, therefore, to curve the wire bonding. Curved wire bonding, in turn, may lead to an unwanted connection to an unrelated data pad. This phenomenon more severely occurs in a mirror chip package.
A solution to the problem is to prepare alternate packages that correspond to the bit organizations or to prepare alternate data pad groups where one of the data pad groups includes data pads arranged for the X8 bit organization and the other includes data pads arranged for the X16 organization. But it is very burdensome to manage memory devices having different pad configurations and different packages having different bit organizations.